How long is the flight and am I flying business or at least economy plus?
Short (<4 hours) flights, I don't have a preference, but tend to prefer earlier in the day because flights that long don't usually take you too far from your time zone and moving in and out of airports at night usually sucks balls.
Long haul, if I'm flying in a human-grade cabin or fare so I can sit comfortably and sleep, red eye flights are tolerable.
By the way, tonight 9pm I'm going on a 27 hour flight(s), which is another beast of it own.
So don't listen to me, really, I'm just talking shit.